Electrical current flow between tunnels for use in heating subsurface hydrocarbon containing formations

Abstract

A system for treating a subsurface hydrocarbon containing formation includes one or more shafts. A first substantially horizontal or inclined tunnel extends from one or more of the shafts. A second substantially horizontal or inclined tunnel extends from one or more of the shafts. Two or more heat source wellbores extend from the first tunnel to the second tunnel. The heat source wellbores are configured to allow electrical current to flow between the heat source wellbores.

1. A system for treating a subsurface hydrocarbon containing formation, comprising:
 one or more shafts; 
 a first substantially horizontal or inclined tunnel extending from one or more of the shafts, wherein the first tunnel is located in an overburden of the formation; 
 a second substantially horizontal or inclined tunnel extending from one or more of the shafts, wherein the second tunnel is located in an overburden of the formation; and 
 two or more heat source wellbores extending between the first tunnel and the second tunnel with a majority of the wellbores located in a hydrocarbon containing layer of the formation, wherein the heat source wellbores are configured to allow electrical current to flow between the heat source wellbores. 
 
     
     
       2. The system of  claim 1 , wherein the electrical current flow between the heat source wellbores is configured to resistively heat the hydrocarbon containing layer. 
     
     
       3. The system of  claim 1 , wherein at least one of the tunnels has an average diameter of at least 1 m. 
     
     
       4. The system of  claim 1 , wherein at least one of the shafts has an average diameter of at least 0.5 m. 
     
     
       5. The system of  claim 1 , wherein at least one of the shafts extends between the surface of the formation and at least one of the tunnels. 
     
     
       6. The system of  claim 1 , wherein at least a portion of the wellbores are located substantially horizontally in the hydrocarbon containing layer. 
     
     
       7. A method for treating a subsurface hydrocarbon containing formation, comprising:
 providing electrical current into two or more heat source wellbores extending between a first substantially horizontal or inclined tunnel and a second substantially horizontal or inclined tunnel, wherein the first and second tunnels are located in an overburden of the formation and a majority of the wellbores are located in a hydrocarbon containing layer of the formation; 
 allowing electrical current to flow between the heat source wellbores; and 
 heating the hydrocarbon containing layer. 
 
     
     
       8. The method of  claim 7 , further comprising heating the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized. 
     
     
       9. The method of  claim 7 , further comprising heating the hydrocarbon containing layer such that at least some hydrocarbons in the hydrocarbon containing layer are mobilized, and producing at least some of the mobilized hydrocarbons. 
     
     
       10. The method of  claim 7 , wherein heating the hydrocarbon containing layer comprises electrical resistance heating of the hydrocarbon containing layer caused by the electrical current flow between the heat source wellbores. 
     
     
       11. The method of  claim 7 , further comprising providing the electrical current into the heat source wellbores and the tunnels through at least one shaft that connects at least one tunnel to the surface of the formation. 
     
     
       12. The method of  claim 7 , wherein at least a portion of the wellbores are located substantially horizontally in the hydrocarbon containing layer. 
     
     
       13. A system for treating a subsurface hydrocarbon containing formation, comprising:
 one or more shafts; 
 a first substantially horizontal or inclined tunnel extending from one or more of the shafts, wherein the first tunnel is located in an overburden of the formation; 
 a second substantially horizontal or inclined tunnel extending from one or more of the shafts, wherein the second tunnel is located in an overburden of the formation; 
 a first heat source wellbore extending from the first tunnel, wherein at least a portion of the first wellbore is located horizontally in the hydrocarbon containing formation, and wherein the first wellbore extends from the overburden of the formation into a hydrocarbon containing layer of the formation; and 
 a second heat source wellbore extending from the second tunnel, wherein at least a portion of the second wellbore is located horizontally in the hydrocarbon containing formation, and wherein the second wellbore extends from the overburden of the formation into a hydrocarbon containing layer of the formation; 
 wherein the heat source wellbores are configured to allow electrical current to flow between the heat source wellbores. 
 
     
     
       14. The system of  claim 13 , wherein the electrical current flow between the heat source wellbores is configured to resistively heat the formation. 
     
     
       15. The system of  claim 13 , wherein at least one of the tunnels has an average diameter of at least 1 m. 
     
     
       16. The system of  claim 13 , wherein at least one of the shafts has an average diameter of at least 0.5 m. 
     
     
       17. The system of  claim 13 , wherein at least one of the shafts extends between the surface of the formation and at least one of the tunnels. 
     
     
       18. The system of  claim 13 , wherein the first heat source wellbore is not connected to the second tunnel. 
     
     
       19. The system of  claim 13 , wherein the second heat source wellbore is not connected to the first tunnel. 
     
     
       20. A method for treating a subsurface hydrocarbon containing formation, comprising:
 providing electrical current into two or more heat source wellbores, at least one wellbore extending from a first substantially horizontal or inclined tunnel in an overburden of the formation into a hydrocarbon containing layer of the formation with at least a portion of the wellbore being horizontal in the formation, and at least one wellbore extending from a second substantially horizontal or inclined tunnel in an overburden of the formation into a hydrocarbon containing layer of the formation with at least a portion of the wellbore being horizontal in the formation; 
 allowing electrical current to flow between the heat source wellbores; and 
 heating the formation. 
 
     
     
       21. The method of  claim 20 , further comprising heating the formation such that at least some hydrocarbons in the formation are mobilized. 
     
     
       22. The method of  claim 20 , further comprising heating the formation such that at least some hydrocarbons in the formation are mobilized, and producing at least some of the mobilized hydrocarbons. 
     
     
       23. The method of  claim 20 , wherein heating the formation comprises electrical resistance heating of the formation caused by the electrical current flow between the heat source wellbores. 
     
     
       24. The method of  claim 20 , further comprising providing the electrical current into the heat source wellbores and the tunnels through at least one shaft that connects at least one tunnel to the surface of the formation. 
     
     
       25. The method of  claim 20 , wherein the at least one wellbore extending from the first tunnel is not connected to the second tunnel. 
     
     
       26. The method of  claim 20 , wherein the at least one wellbore extending from the second tunnel is not connected to the first tunnel.